To sterilize microbially contaminated materials such as packaged goods and hospital materials such as towels, sheets, tubing and the like, it is known to treat the materials with a gaseous chemical sterilant. Especially useful are alkylene oxides, e.g., ethylene oxide and propylene oxide. The contaminated materials are contacted in a sterilization chamber with the chemical sterilant at reduced pressure and moderately elevated temperature for sufficient time to sterilize the material. Useful procedures for sterilizing with gaseous chemical sterilants are disclosed, for example in the present inventor's earlier U.S. Pat. Nos. 4,770,851; 4,812,292; and 4,822,563 the disclosures of which, including cited references, are incorporated herein by reference.
Although the alkylene oxides are excellent sterilants, they are flammable, and, under certain conditions, highly explosive. In addition, they may be toxic.
To reduce the danger of using large containers of flammable gaseous sterilants, a common practice has been to provide the sterilization chamber with a small pressurized container or cartridge filled with a unit dosage, e.g., 200 to 250 g, of the flammable sterilant. After each sterilization run, the empty unit dosage cartridge is replaced for the next run with a full cartridge. An advantage of this procedure is that, in the event of a fire, earthquake or other calamity that might cause rupture of a bulk container of ethylene oxide feeding in the sterilization chamber and consequent fire or explosion, only a small amount of the gaseous chemical is present in or near the sterilization chamber.
Unfortunately, the use of small sterilizing gas cartridges does not eliminate all danger. In fact, the common practice of storing a supply of unit dose cartridges at a hospital or factory creates the danger of multiple explosions should a fire occur in the storage place. The unit dosage cartridges do not have pressure relief devices, as do the bulk shipping containers for ethylene oxide that are approved by the U.S. Department of Transportation (DOT). Each cartridge, in effect, is potentially a small bomb. In addition, the disposable cartridges are costly and their use is more expensive than dispensing from a bulk container such as the conventional shipping cylinders that are specially designed for the rigors of shipping. Furthermore, the cartridges must be disposed of as a hazardous material. Their disposal creates an ecologically undesirable landfill waste.
A need exists, therefore, for an improved apparatus and procedure for feeding unit dosages of a gaseous chemical sterilant economically to a sterilizing apparatus with reduced risk of deflagration of the sterilant or of release of toxic materials to the atmosphere. The present invention provides such an improved apparatus and procedure.